Sonar devices referred to as "fish finders" or "depth sounders" have been available for some time which are designed to provide the user with a generalized "picture" of what is under a boat or other vessel, based on the return signals produced in response to sonar transmissions into the water under the boat. However, it has only been through the use of complex and expensive "scanning" sonar systems that a fisherman has been able to tell where the fish are located below the boat and thus to determine the best side of the boat to fish from. Prior art systems have been developed which permit the fisherman to "aim" or otherwise direct sonar transducers in different directions to manually scan for fish but such systems are obviously cumbersome and inconvenient for use by a fisherman.
Scanning sonars such as those referred to above generally require mechanical rotation of a transducer within a housing to effect scanning or electrically switching between, and/or otherwise changing the phase relationship between, a plurality of transducers arranged in a hemispherical array so that as each transducer of the array is activated in turn, scanning is provided. The resultant information is then displayed on cathode ray tube or a similar display device and this display usually involves the provision of a sweeping pattern on the face of the display device which corresponds to the sweep of the transducer. Other sonar systems have also been provided which use multiple transducers oriented in different directions into the body of water under the boat and thus provide directional information in this way.